Interlock safety device for machinery

ABSTRACT

A control box interposed between the power source for a machine and a machine prevents the delivery of power to the machine until all machinery guards associated with the machine are in a closed circuit position. The control box includes a series of standard sockets, one socket associated with each machinery guard. The control device operates to open a circuit breaker in the power supply line whenever the machinery guards are open or opened.

United States Patent 1191 Huigens 51 May 1, 1973 INTERLOCK SAFETY DEVICEFOR 3,300,009 I/ 1967 Hess ..192/134 X MACHINERY 3,389,628 6/1968 Bankset a]. ..192/134 x 2,487,182 12/1969 Grundy [92/1 34 X [75] Inventor.Wilfred J. HuIgens, Clarmda, Iowa 3,662,369 5/1972 Vinsani 6t aim iZOO/I67 A X Assignge; Lisle Corporation clarinda I w 3,343,158 9/1967Tellerman R X [22] Filed: 1972 Primary Examiner-Allan D. Herrmann Appl.No.: 228,692

Attorney-A. W. Molinare et al.

[5 7] ABSTRACT A control box interposed between the power source for amachine and a machine prevents the delivery of power to the machineuntil all machinery guards associated with the machine are in a closedcircuit position. The control box includes; a series of standardsockets, one socket associated with each machinery guard. The controldevice operates to open a circuit breaker in the power supply linewhenever the machinery guards are open or opened.

2 Claims, 2 Drawing Figures Patnted Ma -11,1973 v 3,730,296

' 1 INTERLOCK SAFETY DEVICE FOR-MACHINERY BACK-GROUND 05 THE INVENTIONIn a principal aspect, the present apparatus is a safety control deviceespecially useful in combination with manufacturing machinery such aspresses.

On Apr. 27, 1971, the United States Department of Labor issued a set ofOccupational Safety and Health Standards pursuant to Section 6(a) of theWilliams SteigerOccupational Safety and Health Act of 1970 84 stat. 1593These standards comprise Part I910 of Chapter I7 of Title 29 of the Codeof Federal Regulanational concensus standards and federal standards forthe safety of materials, machinery and processes utilized by Americanindustry.

Subpart O of these rules and regulations is particularly pertinent tothe present application. In subpart O, numerous standards, rules andregulations are set forth regarding the requirement for guards on powermachinery such as presses. The number and placement of such guards,which are known to those skilled in the art of machinery, isstandardized by these rules.

Needless to say, the utilization of guards has in the past been somewhatlax since there were no specific standards and requirements for the useof such guards. I

Nonetheless, many manufacturers use such guards if V for no other reasonthan to protect their employees and moving piece of machinery. Anelectrical circuit is completed only if the guard is in its closedposition. Only if the electric circuit is completed can the machinery bemade to operate. Otherwise, power will not be supplied to the machinery.Typical prior art references which disclose this general concept includeBanks et a1. U.S. Pat. No. 3,389,628; -Tilbury U.S. Pat. No. 3,l03,270;Hess U.S. Pat. No. 3,300,009; Brown U.S. Pat. No. 3,276,557; Adamsv etal. U.S. Pat. No. 3,181,035; and Holland U.S. Pat. No. 3,311,794.

A feature which is common to all of the aboveidentified patents is thateach guard system is unique to the specific machine and operation ofthat machine. Thus, it becomes desirable to provide an apparatus whereinthe guards may be changed easily without unnecessary delay and extensiverewiring.

SUMMARY OF THE INVENTION propriate sockets in the control box mechanismof the present invention.

It is thus an object of the present invention to provide an improvedcontrol box mechanism which may be utilized in combination with guardsand machinery on which the guards are to be'used.

It is a further object of the present invention to provide a standardand modular system for utilizing guards with any machinery and with anyguards used in association with that machinery.

Still another object of the present invention is to provide a system forattaching and utilizing guards in association with machinery inaccordance with Federal Occupational Safety and Health Standards whichsystem is simple, economic and easy to incorporate with existingmachinery.

These and other objects, advantages and features of the presentinvention will be set forth in greater detail in the description whichfollows.

BRIEF DESCRIPTION OF THE DRAWING In the detaileddescription whichfollows, reference will be made to thedrawing comprised of the followingFIGURES: Y I

FIG. 1 is an electrical schematic of the control mechanism or controlbox of the present invention as utilized in association with a piece ofpower equipment and guards associated with that equipment; and

, FIG. 2 is a perspective view of the improved control box of thepresent invention in combination with a schematic guard.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the FIGS. 1 and .2,the safety control mechanism of the present invention is housed in anenclosure or housing 10 illustrated schematically in FIG. 1 by thedashed line. Alternating current from a source 12 flows through leadwires 14 and 16 into the housing 10. Of course, the wires 14 and 116 areinsulated from the housing 10. The voltage supplied through the wires 14and 16 is a generally high voltage, for example, 120

volts a.c. or more. Within the housing 10, the hot lead wire 14 isspliced and connected with a primary coil 18 of a transformer 20. Theopposite side of the coil 18 is grounded.

Transformer 20 is a step-down transformer wherein the primary coil 18i'sgenerally in parallel with a normally open circuit breaker switch 22within the enclosure 10 and a machine schematically illustrated by theresistor 24. That is, the resistor 24 represents the load on the powerline resulting from operation of a machine, for example, a stampingpress or the like.

Typically, the machine would include a number of moving parts which asstated above under new federal regulations require certain guards. Aguard 26 is schematically illustrated in FIG. 1 in a closed guardposition. In FIG. 2, guard 26 is illustrated in the open circuitposition, that is, before the guard 26 is properly placed on a machineor properly closed over the moving part on that machine. The'use ofguards and their placement on machines is well known to those skilled inthe art. I

The transformer also includes a secondary coil 28 which is one of anumber of electric elements in series in a controlv circuit '30illustrated generally by the dotted line in FIG. 1. The transformer 20steps down voltage to a small control circuit amount, say 12 volts, tofurther accentuate the safety features of the apparatus. Also includedas part of the control circuit 30 are a plurality of sockets 32-36 whichare connected in series with coil 28 and with a solenoid coil 38associated with the normally open circuit breaker 22. A plurality ofshunt switches 40-44 are associated with each of the sockets 3236respectively. Closing one of the shunts as at 40 permits shortcircuiting the control effect attributable to the associated socket 32.

Lead wires from an appropriate mating plug associated with a guard, asat 26, connect with the leads of a socket as for example socket 35 inFIG. 1. Thus, a circuit may be completed through the coil 28,appropriate shunts 40-44 and appropriate sockets 32-36 and guards 26 toenergize the coil 38 and thus close the normally open circuit breaker22. This permits a flow of power to the machine 24.

A telltale light 46 is arranged in parallel with the sockets 32-36 andtheir associated shunts 40-44 respectively. Operation of the light 46 isalso responsive to the movable element of the breaker 22 so that currentflow through coil 38 will cause the light 46 to be activated. Thus, ifthere is a failure in the system, one can tell at a glance whthe'r thefailure is in the control mechanism illustrated schematically in FIG. 1.If the light is not lit, then power is not being supplied to the machine24 On the other hand, if the light is lit, and the machine does notoperate, then the machine is faulty.

The apparatus has many advantages and modifications. For example, thesockets as at 32 may have geometrical openings which are unique and canreceive only plugs associated with desired guards.

4 Also, after a short press run, it is possible to manipulate and alterthe position of guards for a new press run without requiring anelectrician to rewire the system.

A preferred embodiment of the present invention is described in thisspecification. Nevertheless, it is to be understood that the inventionshall be limited only by the following claims and their equivalents.

What is claimed is: I

1. An interlock safety device to be utilized in combination withmachinery guards and a machine upon which said guards are mountedcomprising, in combination:

an enclosure;

an alternating current electrical power supply line ries in said lowvoltage control circuit, said low voltage control circuit including inseries said secondary coil, a plurality of sockets for machinery guards,a shunt for each of said sockets, and a solenoid coil for said normallyopened power supply circuit breaker, said power supply circuit breakerbeing closed whenever power is on to said supply line and said socket isshunted or has closed machinery guards plugged therein.

2. The device of claim 1 including a telltale light in parallel withsaid plurality of sockets.

1. An interlock safety device to be utilized in combination withmachinery guards and a machine upon which said guards are mountedcomprising, in combination: an enclosure; an alternating currentelectrical power supply line into said enclosure, said power line beingthe power line for said machine; a normally open circuit breaker in saidpower supply line and mounted in said enclosure, said circuit breakerbeing in series with said machine whenever said device is used incombination with said machine; a low voltage control circuit mounted insaid enclosure; a step-down transformer mounted in said enclosure andhaving a primary in parallel with said normally open circuit breaker andhaving a secondary in series in said low voltage control circuit, saidlow voltage control circuit including in series said secondary coil, aplurality of sockets for machinery guards, a shunt for each of saidsockets, and a solenoid coil for said normally opened power supplycircuit breaker, said power supply circuit breaker being closed wheneverpower is on to said supply line and said socket is shunted or has closedmachinery guards plugged therein.
 2. The device of claim 1 including atelltale light in parallel with said plurality of sockets.